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No return line in fuel circuit?

in 912 / 914 Technical Questions 11 years ago

  • Re: No return line in fuel circuit?

    by » 11 years ago

    The old pumps aren't like the new pumps. They do many times put out more pressure. I see a number of people with vapor lock or more correctly not lock, but vapor in the fuel lines after the plane has run and sits on the ground for 45 minutes - 1 hr. with a nice tight cowl. Starting it up and let it run at about 2200-2400 rpm or while you taxi out from parking should run some cooler fuel through and the fuel pressure should return to normal. A return line is simple enough to install and can go to more than one location. If it were me I would put one in. just remember the return line has a .035 restricting orifice in it.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

    Thank you said by: Kenneth Hagesten
      
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  • Re: No return line in fuel circuit?

    by » 11 years ago

    Sorry, i am old in the game, and when i bought my aircraft (Seaplane on floats) nobody had return lines, and because i am not operating from an airfield i have not had much contact with other flyers and have therefor never heard about return lines. So i have very bad knowledge about these issues.

    Could i ask you to explain to me when fuel goes back in the return line. Is it under standstill after a flight? Or is it during a flight? And so under which conditions? And how much fuel could it be at such occasions that enters the return line?

    Another question i have is following. I have also never had an auxiliary electric fuel pump. But now i am going to install one. If i choose to not install the new Corona pump would not an extra electric fuel pump help there in case there would be some malfunction with my old mechanic fuel pump? I do not know why Rotax recommends shifting to the new Corona pump. What malfunction could happen to them? After all it is only a recommendation and not mandatory to shift to the new fuel pump. Or is it better anyway to install the new Corona pump. It is not that expensive and it is easy to install. It is only irritating for me to install a new pump when i have operated this old one only one year. I thought that i could wait until the five years has gone before i shift to the new Corona pump.

    Well that was many questions but i hope you can bear with me.

    Kenneth
      
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  • Re: No return line in fuel circuit?

    by » 11 years ago

    Roger,

    You said the return line could go to more than one place...Could you list those places ?

    I originally had no return line, but just installed one to the gascolator which is before my electric and mechanical pump. Since installation, on another forum, someone said it should not go there because there is no place for the vapor to escape. Do you agree with this, or is the gascolator an acceptable place to run the return line. if it is, where does the vapor go ???

    Thanks, Jim
      
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  • Re: No return line in fuel circuit?

    by » 11 years ago

    Hi James,

    The gascolator is just fine. I know two aircraft companies that have been doing it that way for 10 years and have had no issues. I have a Flight Design CT and that is where they have always installed it and never has an issue and they have more SLSA aircraft out there than most. Vapor will just hit the cooler fuel and just be absorbed back into the fuel. There isn't that much to make a huge difference by the time it hits the cooler fuel. It can go into a header tank, a wing tank, a supply line or the gascolator.
    Remember to put the #35 Mikuni pilot or idle jet in the fitting for the correct restrictive fuel flow. The #35 Mikuni jet is based on fuel flow amount and not a specific orifice size. The Installation manual says a .35mm, but it is a #35 Mikuni idle jet that passes a known quantity of fuel.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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  • Re: No return line in fuel circuit?

    by » 11 years ago

    But I going to make return line from 5 port splitter after fuel pomp. I have to use special reductor.
    You probably talking about drain hole in fuel pump. I thing you shouldn't see any fuel in this place.
    If you are thinking about return line form star 5 port splitter you can't put this line out of plane. You'll loose your fuel.
      
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